The invention relates to improvements in valves of the type wherein a shank or a stem is anchored in a disc-shaped or otherwise configurated valving element. More particularly, the invention relates to improvements in devices for rotatably coupling the shank and the valving element of a valve or another flow regulating element to each other.
German Utility Model No. 19 56 491 discloses a valve wherein the valving element has a tubular extension for one end section of a shank. The end section has an annular shoulder between a larger-diameter portion and a smaller-diameter portion, and such shoulder is engaged by a two-piece ring which is confined in the socket of the extension so that the valving element and the shank can rotate relative to each other. The extension is deformed in a region adjacent to the ring so that the latter cannot be extracted from the socket.
The ring which is used in the valve of the Utility Model comprises two pieces of jointly drilled semiround steel stock. The main retaining or holding action takes place at the end faces of the ring. One end face abuts a shoulder of the valving element and the other end face abuts a shoulder of the shank. A drawback of such proposal is that, in order to enlarge the area of contact between one end face of the ring and the shoulder of the shank, it is necessary to provide the shank with a relatively large radially extending annular shoulder which can affect the stability of the shank and of the assembled valve. Moreover, and since the transition from the shoulder to the periphery of the adjacent cylindrical portion of the shank is very pronounced, such region of the shank is subjected to substantial impact stresses which can lead to a breakage of the shank at its shoulder. The utilization of a concave shoulder on the shank would merely lead to a reduction of the stress-receiving area of such shoulder, i.e., the depth of the cut which is required to make the shoulder would have to be increased with attendant additional weakening of the shank. Still further, the specially designed two-piece ring is expensive and its insertion into the socket of the extension is a complex procedure.